The present invention relates generally to a braided rope construction and is more particularly concerned with a novel and improved double braid, i.e. rope or cordage having a braided core with a braided cover formed thereover.
Double braided ropes of this general type are known in the prior art and the braided cord disclosed in Fogden U.S. Pat. No. 3,035,476 issued May 22, 1962 is an example of the type of double braid with which the present invention is concerned, and furthermore represents what is thought to be the closest prior art.
In the Fogden patent, the braided cover is made by braiding a plurality of "singles" yarns in such a manner that the individual fibers or filaments which make up the "singles" yarns extend in a direction substantially parallel to the axis of the rope, which has been found to create less friction when the rope is passed through or chock or is otherwise moved axially while in frictional contact with some other object, thus resulting in less snagging of the individual filaments or fibers, thereby promoting longer rope life. This is accomplished in the Fogden patent by twisting together a plurality of individual fibers or strands to form what is known as a "singles" yarn and then braiding a plurality of said "singles" yarns in such a manner that the direction of twist of the individual fibers and their respective "singles" yarns is equal and opposite to the direction of its respective "singles" yarns in the braid, the result being that the individual fibers or filaments extend substantially parallel to the axis of the rope.
In the double braided rope of Fogden, the individual fibers or filaments which are twisted together to make up a "singles" yarn comprise a large bundle of fibers tightly twisted together. This hard, tight twist of the individual filaments or fibers is required to properly hold the fibers together so as to minimize or prevent snagging, thereby increasing wear life, and also is required in order to assure that the fibers lie parallel to the axis of the rope, so as to minimize friction when the rope is passed through a chock or the like. However, it is important to understand that this hard, tight twist of the individual fibers increases the length of fiber in a given length of braid, thereby increasing the stretch of the rope as load is applied thereto, which is an extremely undesirable characteristic, particularly where the rope is being used for yachting purposes or the like, which is a common usage for double braided ropes of this type. In addition, the hard, tight twist of the individual fibers or filaments minimizes the exposed outer surface of the filaments, i.e. "rounds up" the yarns, thus reducing the bearing surface of the rope and making it harsher to the hands when handled.
It is therefore a primary object of the present invention to provide a braided rope of the general type described in which the individual fibers in the rope lie straighter, i.e. follow a shorter path in the braid, whereby substantially less stretch of the braided rope results from a given load, when compared, for example, to the type of rope shown in the aforesaid Fogden patent.
Another object of my invention is the provision of a braided rope of the character described having a greater outer bearing surface, thus distributing the wear over a larger area, and at the same time, resulting in a smoother surface that is more comfortable when gripped by a person's hands.
A further object is the provision of a rope with the characteristics described wherein the individual fibers or filaments are "locked in" or twisted together in relatively small bundles, thus resulting in less likelihood of snagging, which in turn increases the wear life of the rope.
The above objectives are achieved by twisting together a relatively small bundle of individual fibers or filaments to form a plurality of "singles" yarns and then twisting together a plurality of said "singles" yarns to form a plurality of "plied" yarns. When the "singles" yarns are twisted together to make up the "plied" yarns, the direction of twist is opposite to the direction of twist of the individual fibers or filaments in their respective "singles" yarns. More specifically, if the individual fibers or filaments are twisted in an "S" direction to make up the "singles" yarns, then the "singles" yarns are twisted in a "Z" direction to form the "plied" yarns, and vice versa.
As a result of this, the individual fibers or filaments, as they exist in the braid, lie rather flat or ribbon-like, since relatively little twist remains in the "singles" yarns. The helical angle which the fibers form as they lie in the braid is relatively open or slack, as compared to other braids, such as that shown in the Fogden patent, where the fibers are tightly twisted, as aforesaid. Since, however, the helical angle of twist of the "singles" yarns within their respective plied yarn is equal and opposite to the helical angle at which the plied yarn lies in the braid, it will be seen that the "singles" yarns extend substantially parallel to the axis of the rope, which is a desirable characteristic.
Thus it might be said that the basic difference between the present invention and the aforesaid Fogden patent is that in Fogden "singles" yarns are braided so that the individual fibers or filaments in the "singles" yarns extend substantially parallel to the axis of the rope, whereas in the present invention "singles" yarns are plied or twisted together to form plied yarns, which are then braided, whereby instead of the individual fibers or filaments extending parallel, it is the "singles" yarns which extend parallel to the axis of the rope. The concept of braiding plied yarns instead of "singles" yarns constitutes a completely novel and unique approach in the manufacture of braided ropes of the type under consideration, and has been found to result in amazing advantages, such as less stretch for a given load, less snagging and hence greater wear life, as well as smoother handling.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.